The tradition argument is meaningless. America has hundreds of cultures within its own borders now, all with different traditions. There are already thousands of churches that can and do marry gay people, the only difference is whether or not the state chooses to acknowledge that marriage with the social benefits. The marriage itself already exists.
If my tax dollars are dolling out benefits to married people (which I already think is wrong, for the record), then I want guarantees that the alotted benefits are given out in a non-discriminatory fashion. If straight people are getting my tax dollars, then I want the gays to get them too. None of this elitist, traditional, la-dee-da hoopla about the constitution which has no basis.
That is, until state legislations created a new right for heterosexuals that didn't exist before.